Single-phase position sensorless permanent magnet motor control apparatus

ABSTRACT

A single-phase permanent magnet motor control apparatus, in particular, a low price, flat output torque, low vibration, low noise single-phase permanent magnet motor control apparatus, and a fan and pump using such a single-phase permanent magnet motor control apparatus are provided. In a single-phase permanent magnet motor control apparatus for driving a single-phase permanent magnet motor by using a DC power supply, a converter for converting DC to AC, and a control circuit for controlling the converter, a motor current measuring unit, a terminal voltage measuring unit, a correction unit for correcting an impedance drop in motor constants, and a calculation unit for finding an induced voltage to be obtained by control are included, and a polarity of a terminal voltage is determined on the basis of a value of the found induced voltage.

BACKGROUND OF THE INVENTION

The present invention relates to a single-phase position sensorlesspermanent magnet motor control apparatus. In particular, the presentinvention provides a low vibration, low noise, small-sized, lightweight, low-cost single-phase position sensorless permanent magnet motorcontrol apparatus which runs and controls a single-phase permanentmagnet motor and consequently which is suitable to mount on a vehiclesuch as an automobile.

The present invention relates to a single-phase permanent magnet motorcontrol apparatus. In particular, the present invention relates to a lowprice, flat output torque, low vibration, low noise single-phasepermanent magnet motor control apparatus, and a fan and a pump usingsuch a single-phase permanent magnet motor control apparatus.

A single-phase permanent magnet motor control apparatus is used as a fandrive source.

As compared with an ordinary three-phase motor, the single-phasepermanent magnet motor control apparatus has one set of windings(whereas three sets are included in the case of the three-phase motor).As for the conversion circuit as well, an H-bridge can be used.Therefore, the number of components becomes four (whereas six componentsare required in the case of the three-phase motor). Thus, thesingle-phase permanent magnet motor control apparatus has a great pricemerit. If a position detector is attached, only one hall element isrequired (whereas three hall elements are required in the case of thethree-phase motor), resulting in a price merit as compared with the caseof the three-phase motor.

On the other hand, in application such as fans where the starting torqueis not large or the rising time is gentle, sensorless drive isconducted. As compared with the established sensorless drive of thethree-phase motor, the sensorless drive of the single-phase permanentmagnet motor becomes conversely complicated, resulting in a problem.

In addition, as compared with the three-phase motor, the single-phasepermanent magnet motor has, in principle, a problem that torquegenerated by a current let flow through single-phase windings andmagnetic flux of the permanent magnets generates two zero or negativetorque regions per cycle in electric angle in at least the rotationdirection. This problem is coped with by exercising control orcontriving the shape of the stator core so as to change the gap lengthof the stator core in the circumference direction, make up for the zeroor negative torque with cogging torque generated by the stator core andthe permanent magnets, and thereby prevent negative torque from beinggenerated.

As for the use, there is a tendency that applications to pumps mainly inautomobiles increase besides the fans. Major reasons of the adoption andexpansion of pump drive using an electric motor are that power savingcontrol can be achieved by exercising motor control instead of pumpdrive using an engine as a measure for improving the fuel expenses orthat pump drive using an engine is restricted by execution of idlingstop. In this case, the low price is very important. In addition, in thecase of the fan or pump, large start torque is not needed and theproblem that the start torque is hard to obtain which is a major problemof the single-phase permanent magnet motor does not matter. Therefore,it is easy to adopt the single-phase permanent magnet motor.

A disclosure example of representative control of sensorless drive ofthe single-phase permanent magnet motor having the price merit is shownin JP-B-7-63232.

According to JP-B-7-63232, the position of the rotor (changeover pointof applied voltage) is detected by providing an energization stop periodnear a changeover point between positive and negative parts of aninduced voltage in the single-phase permanent magnet motor, generatingan induced voltage between windings, and discriminating whether theinduced voltage is positive or negative.

In addition, a single-phase permanent magnet motor control apparatus isused as the fan drive source because of its low price. The single-phasepermanent magnet motor has, in principle, a problem that torquegenerated by a current let flow through single-phase windings andmagnetic flux of the permanent magnets generates two zero or negativetorque regions per cycle in electric angle in at least the rotationdirection. This problem is coped with by exercising control orcontriving the shape of the stator core so as to change the gap lengthof the stator core in the circumference direction, make up for the zeroor negative torque with cogging torque generated by the stator core andthe permanent magnets, and thereby prevent negative torque from beinggenerated.

As compared with an ordinary three-phase motor, the single-phasepermanent magnet motor control apparatus has one set of windings(whereas three sets are included in the case of the three-phase motor).As for the conversion circuit as well, an H-bridge can be used.Therefore, the number of components becomes four (whereas six componentsare required in the case of the three-phase motor). Thus, thesingle-phase permanent magnet motor control apparatus has a great pricemerit. If a position detector is attached, only one hall element isrequired (whereas three hall elements are required in the case of thethree-phase motor), resulting in a price merit as compared with the caseof the three-phase motor. On the other hand, there are drawbacks thatthe output torque at the time of operation is hard to become flat andvibration noise is apt to occur because of restrictions described above.

As for the use, there is a tendency that applications to pumps mainly inautomobiles increase besides the fans. Major reasons of the adoption andexpansion of pump drive using an electric motor are that power savingcontrol can be achieved by exercising motor control instead of pumpdrive using an engine as a measure for improving the fuel expenses orthat pump drive using an engine is restricted by execution of idlingstop. In this case, the low price is very important. In addition, in thecase of the fan or pump, large start torque is not needed and theproblem that the start torque is hard to obtain which is a majordrawback of the single-phase permanent magnet motor does not matter.Therefore, it is easy to adopt the single-phase permanent magnet motor.

A disclosure example of representative control in the single-phasepermanent magnet motor is shown in JP-A-2004-88870. In the exampledisclosed in JP-A-2004-88870, it is attempted to reduce torque ripple byplacing restrictions in two places where the current becomes large inhalf electrical cycle of the motor in order to reduce the torque rippleof the single-phase permanent magnet motor.

SUMMARY OF THE INVENTION

According to JP-B-7-63232, the position of the rotor is detected byproviding an energization stop period near a changeover point betweenpositive and negative parts of an induced voltage in the single-phasepermanent magnet motor, generating an induced voltage between windings,and discriminating whether the induced voltage is positive or negative.As a result, the polarity of the applied voltage capable of generatingpositive torque can always be confirmed, and consequently sensorlessdrive can be conducted. Basically in this scheme, however, a quiescentperiod of a current for outputting an induced voltage on the windings isprovided. Therefore, there is a fear that efficiency drop and anincrease in pulsating torque might be caused, resulting in a motoryielding large noise and vibration.

Therefore, an object of the present invention is to provide a low noise,low vibration single-phase permanent magnet motor control apparatus thateliminates the problems of the conventional art described heretofore andthat is little in efficiency falling and a fan or pump using thesingle-phase permanent magnet motor control apparatus.

The example described in JP-A-2004-88870 brings about an effect that thetorque ripple is reduced to some extent with a simple configuration.

When the number of revolutions has changed, when the load has changed,or when the temperature has changed, however, it cannot be coped withsufficiently and there is a fear that torque ripple might be generatedresulting in vibration and noise.

Therefore, another object of the present invention is to solve theproblems of the conventional art described heretofore, cope with loadvariation to some extent, reduce the torque ripple, and thereby providea low vibration, low noise, low cost single-phase permanent magnet motorcontrol apparatus and a fan and a pump using the single-phase permanentmagnet motor control apparatus.

An aspect of the present invention provides a single-phase positionsensorless permanent magnet control apparatus for controlling a powerconverter which drives a single-phase permanent magnet motor includes amotor current measuring unit, the single-phase position sensorlesspermanent magnet control apparatus providing a terminal voltagemeasuring unit, a correction unit for correcting an impedance drop inmotor constants, and a calculation unit for finding an induced voltageto be obtained by control, wherein a polarity of a terminal voltage isdetermined on the basis of a value of the found induced voltage.

As a result, it is possible to provide a low torque ripple, low noise,low vibration, high efficiency single-phase position sensorlesspermanent magnet motor.

Another aspect of the present invention provides a single-phasepermanent magnet motor control apparatus for controlling a powerconverter to drive a single-phase permanent magnet motor which includesa rotor having permanent magnets and a stator having single-phasewindings and which generates cogging torque by magnetic action betweenthe rotor and the stator, wherein the single-phase permanent magnetmotor control apparatus comprises cogging torque and induced voltagewaveform information of the single-phase permanent magnet motor.

As a result, it is possible to provide a low vibration, low noise, lowcost single-phase permanent magnet motor control apparatus, and a fanand a pump using the single-phase permanent magnet motor controlapparatus.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a single-phase position sensorless permanent magnet motordrive circuit in an embodiment according to the present invention;

FIGS. 2A to 2F show operation explanation diagrams of the embodimentaccording to the present invention;

FIGS. 3A to 3D show operation explanation diagrams of another embodimentaccording to the present invention;

FIG. 4 shows a single-phase permanent magnet motor drive circuit instill another embodiment according to the present invention;

FIG. 5 shows details of a principal part in the still another embodimentaccording to the present invention;

FIGS. 6A to 6H show operation explanation diagrams of the still anotherembodiment according to the present invention;

FIG. 7 shows details of a principal part in yet another embodimentaccording to the present invention; and

FIGS. 8A to 8I show operation explanation diagrams of the still anotherembodiment according to the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows a configuration of a single-phase position sensorlesspermanent magnet motor control apparatus according to an embodiment ofthe present invention. FIGS. 2A to 2F show its operation explanationdiagrams.

In FIG. 1, a single-phase position sensorless permanent magnet motorcontrol apparatus 1 includes a single-phase permanent magnet motor 2, aconversion circuit 5 which functions to supply AC power from a DC powersupply Edc to the single-phase permanent magnet motor 2, and a controlcircuit 6 which controls an output current of the conversion circuit 5.

The single-phase permanent magnet motor 2 includes a stator 3 and arotor 4. In the ensuing description, it is supposed that the motor isthe so-called outer rotor type motor in which the stator 3 is disposedon an inner circumference and the rotor 4 is disposed on an outercircumference. However, similar description holds true of the innerrotor type motor or other motors. In the shown example, the number ofpoles of the permanent magnets in the rotor 4 is four. However, theeffects of the present invention do not depend upon the number of poles.

In FIG. 1, the stator 3 includes a stator core 9, stator windings 10wound around the stator core 9, and its supporting device (notillustrated). Typically, the stator core 9 is formed by stamping outthin silicon steel plates and laminating them. However, the stator core9 may be formed of dust core. As illustrated, the number of salientpoles is four, and it is made equal to the number four of permanentmagnets 7 in the rotor 4. Four stator windings 10 are connected inseries and connected to the conversion circuit 5 as illustrated.

The rotor 4 includes permanent magnets 7 and a rotor core 8 disposedaround the permanent magnets 7 to constitute a magnetic circuit for thepermanent magnets 7 and fulfill a role of mechanical coupling to anoutput shaft (not illustrated). As for the magnets, ferrite rubbermagnets or plastic magnets are typically used because of their lowprices.

In FIG. 1, the gap face of the stator core 9 is selected with respect tothe gap between the rotor 4 and the stator 3 as follows: the surface ofthe stator core 9 in the rotation direction is determined as indicatedby 92 so as to have a nearly constant small gap length, whereas thesurface of the stator core 9 in the anti-rotation direction (herein, therotor 4 is supposed to rotate in the counterclockwise direction) isdetermined as indicated by 91 so as to have a gradually increasing gaplength. In principle, in the single-phase permanent magnet motor, torquegenerated by a current let flow through single-phase windings andmagnetic flux of the permanent magnets generates two zero or negativetorque regions per cycle in electric angle in at least the rotationdirection. By taking the above-described shape, cogging torque that canmake up for the zero or negative torque can be generated effectively,resulting in low vibration and low noise.

In a typical single-phase permanent magnet motor, a position detector isdisposed on the stator 3 so as to be located near the shaft end of eachof the permanent magnets 7 in the rotor 4. (Typically, a hall element isused to detect the magnetic flux of the permanent magnet 7.) Theposition detector functions to detect the position of the permanentmagnet 7 and let flow an effective current through the single-phasepermanent magnet motor 2 via the conversion circuit 5. In applicationssuch as automobiles, however, the use environment is high in temperatureand hall elements cannot be used in some cases. If it is difficult todispose the position detection elements because of circuit mounting, thesenseless drive scheme described in the disclosure example isconceivable.

In accordance with an aspect of the present invention, a control circuit6 includes an induced voltage calculation unit 14 for calculating aninduced voltage of the single-phase permanent magnet motor 2 on thebasis of information of a current sensor 16 and previously storedwinding resistance information 11 and inductance information 12 of thestator windings 10, a velocity control circuit 13, and a drive signalcomputing and producing circuit 15 for synthesizing signals from thevelocity control circuit 13 and so on. In accordance with the presentinvention, the position of the rotor is determined and timing of appliedvoltage is determined on the basis of information obtained by theinduced voltage calculation unit 14. As a result, continuousenergization is possible and single-phase sensorless operation withlittle torque ripple is made possible. Therefore, magnetic pole positiondetectors are made unnecessary and sensorless operation is madepossible.

Hereafter, operation in the present invention will be described withreference to FIGS. 2A to 2F.

FIGS. 2A to 2F are operation explanation diagrams of the above-describedcontrol in the present invention.

FIG. 2A shows a terminal voltage Et(θ) of the motor. The magnitude ofthe terminal voltage is regulated by PWM (Pulse Width Modulation) or thelike. PWM between positive and negative half cycles is typically madeconstant. By the way, it is also possible to make the terminal voltagelead or lag behind an induced voltage shown in FIG. 2B by causing adelay of a fixed time from a zero crossing point. It is also possible tohave the value of the terminal voltage Et(θ) in a microcomputer.

FIG. 2C shows the induced voltage as a function of the rotationelectrical angle.

The induced voltage has a feature that the waveform is bilaterallyasymmetric because of the shape of the stator core on the gap face. Theinduced voltage calculation unit 14 calculates an induced voltage E0(θ)according to the following equation by using information of the terminalvoltage Et(θ), a current i(θ) of a current sensor, winding resistance rand winding inductance L.

$\begin{matrix}{{{EO}(\theta)} = {{{Et}(\theta)} - {\left( {r + L} \right)\frac{{i(\theta)}}{t}}}} & (1)\end{matrix}$

where

Et(θ) is the terminal voltage shown in FIG. 2A,

r is winding resistance,

L is winding inductance, and

i(θ) is a current value measured by the current sensor 16.

FIG. 2B shows the current i(θ) which is taken in from the current sensor16.

FIG. 2D shows cogging torque Tcog(θ). This is generated by the shape ofthe gap face of the stator core, the size of the slit between statorsalient poles, and magnetic action with the magnetic flux distributionof the permanent magnets.

FIG. 2E shows electromagnetic torque Tw(θ) which is generated by themagnetic flux (induced voltage) generated by the permanent magnet and acurrent which flows through the stator windings. The electromagnetictorque Tw(θ) can be calculated by using the following equation.

$\begin{matrix}{{{Tw}(\theta)} = \frac{{{EO}(\theta)}{I(\theta)}}{\omega}} & (2)\end{matrix}$

where

ω represents information of rotation angular velocity,

E0(θ) represents induced voltage information for an angle θ at eachvelocity ω, and

I(θ) represents current information obtained by the current sensor.

FIG. 2F shows total torque Tt(θ). The total torque Tt(θ) can becalculated by using the following equation as the sum of theelectromagnetic torque Tw(θ) and the cogging torque Tcog(θ).

Tt(θ)=Tcog(θ)+Tw(θ)   (3)

where Tcog(θ) represents the cogging torque for the rotation angle.

In accordance with the present invention, the single-phase permanentmagnet motor shown in FIG. 1 is typically controlled by the velocitycontrol circuit 13 to follow a velocity command Ns. For exercising thevelocity control, velocity information of the single-phase permanentmagnet motor becomes necessary. On the basis of induced voltageinformation obtained by the induced voltage calculation unit 14,velocity feedback information is calculated from a period of one cyclein electrical angle. Constant velocity control is exercised by utilizingthe velocity feedback information and using proportional integralcontrol according to the velocity error as occasion demands. The motorcan be controlled to have the velocity Ns by the control describedheretofore.

In accordance with the present invention, the positive-negativechangeover of the terminal voltage Et(θ) is conducted on the basis ofthe induced voltage information obtained by the induced voltagecalculation unit 14 according to the equation (1). For example, theterminal voltage is changed over from positive to negative when theinduced voltage falls from a highest positive part and reaches apredetermined value or less. The terminal voltage thus controlled isshown in FIG. 2A.

The voltage is controlled to become constant until the next changeoverpoint. As occasion demands, however, it is also possible to provide therising part or the falling part with a voltage change near thechangeover point. The current can be controlled continuously by suchcontrol.

FIGS. 3A to 3D are operation explanation diagrams of another embodimentaccording to the present invention.

Since the current quiescent period for detecting the terminal voltage isprovided during half cycle, a steep torque change occurs in the outputtorque. Furthermore, since the current stop period is provided, itbecomes necessary to increase the current in other energization periods,resulting in a lowered efficiency.

As a result of the control described heretofore, it is possible toprovide a low torque ripple, low noise, low vibration, high efficiencysingle-phase position permanent magnet motor.

In this way, the present invention provides a single-phase permanentmagnet motor control apparatus for driving a single-phase permanentmagnet motor by using a DC power supply, a converter for converting DCto AC, and a control circuit for controlling the converter, wherein amotor current measuring unit, a terminal voltage measuring unit, acorrection unit for correcting an impedance drop in motor constants, anda calculation unit for finding an induced voltage to be obtained bycontrol are included, and a polarity of a terminal voltage is determinedon the basis of a value of the found induced voltage. As compared withan ordinary three-phase motor, therefore, only one set of windings andone hall element are required as shown in FIG. 1 (whereas three sets arerequired in the case of the three-phase motor). As for the conversioncircuit as well, an H-bridge can be used. Therefore, the number ofcomponents becomes four, resulting in a great price merit. On the otherhand, owing to the above-described control, the operation torque can beflattened and a low noise, low vibration permanent magnet motor controlapparatus that compares favorably with the three-phase motor can beprovided.

By using the single-phase permanent magnet motor control apparatus in anelectromotive fan and electromotive pump, it is possible to provide alow price, small-sized, light weight, low noise, low vibrationelectromotive fan and electromotive pump with a single configuration.(For example, when the fan and pump are disposed in a passenger room ofa vehicle, the low noise and low price form powerful weapons.)

Description has been given heretofore with a mind to a system using amicrocomputer as the control circuit 6. However, it is possible toimplement a single-phase position sensorless permanent magnet motorcontrol apparatus having the control circuit 6 which includes theinduced voltage calculation unit 14, even if the control circuit 6 isconstituted by using a discrete circuit including amplifiers, resistorsand capacitors. In this case, the single-phase position sensorlesspermanent magnet motor control apparatus can be implemented with a moreinexpensive configuration.

At the time of start, there is no information of induced voltage and thevoltage energizing method is unknown. However, a mechanism for lettingflow a current through the stator windings is included. As a result,stable start can be made possible by utilizing polarity discriminationfor discriminating a current direction in which the rotor can outputpositive torque.

FIG. 4 shows a configuration of a single-phase permanent magnet motorcontrol apparatus according to still another embodiment of the presentinvention. FIG. 5 shows details of its principal part. FIGS. 6A to 6Hshow its operation explanation diagrams.

In FIG. 4, a single-phase permanent magnet motor control apparatus 101includes a single-phase permanent magnet motor 2, a conversion circuit 5which functions to supply AC power from a DC power supply Edc to thesingle-phase permanent magnet motor 2, and a control circuit 6 whichcontrols an output current of the conversion circuit 5.

The single-phase permanent magnet motor 2 includes a stator 3 and arotor 4. In the ensuing description, it is supposed that the motor isthe so-called outer rotor type motor in which the stator 3 is disposedon an inner circumference and the rotor 4 is disposed on an outercircumference. However, similar description holds true of the innerrotor type motor or other motors. In the shown example, the number ofpoles of the permanent magnets in the rotor 4 is four. However, theeffects of the present invention do not depend upon the number of poles.

In FIG. 4, the stator 3 includes a stator core 9, stator windings 10wound around the stator core 9, and its supporting device (notillustrated). Typically, the stator core 9 is formed by stamping outthin silicon steel plates and laminating them. However, the stator core9 may be formed of dust core. As illustrated, the number of salientpoles is four, and it is made equal to the number four of permanentmagnets 7 in the rotor 4. Four stator windings 10 are connected inseries and connected to the conversion circuit 5 as illustrated.

The rotor 4 includes permanent magnets 7 and a rotor core 8 disposedaround the permanent magnets 7 to constitute a magnetic circuit for thepermanent magnets 7 and fulfill a role of mechanical coupling to anoutput shaft (not illustrated). As for the magnets, ferrite rubbermagnets or plastic magnets are typically used because of their lowprices.

In FIG. 4, the gap face of the stator core 9 is selected to take a shapeso that the gap between the rotor 4 and the stator 3 will become nearlyconstant in the rotation direction and the gap will gradually increasein the anti-rotation direction (herein, the rotor 4 is supposed torotate in the counterclockwise direction). In particular, the gap faceof the stator core 9 is determined so as to have a large gap length asindicated by 91 in the anti-rotation direction of the stator core 9 andhave a nearly constant small gap length as indicated by 92 in therotation direction. In principle, in the single-phase permanent magnetmotor, torque generated by a current let flow through single-phasewindings and magnetic flux of the permanent magnets generates two zeroor negative torque regions per cycle in electric angle in at least therotation direction. By taking the above-described shape, cogging torquethat can make up for the zero or negative torque can be generatedeffectively, resulting in low vibration and low noise.

A position detector 111 is disposed on the stator 3 so as to be locatednear the shaft end of each of the permanent magnets 7 in the rotor 4.(Typically, a hall element is used to detect the magnetic flux of thepermanent magnet 7.) The position detector 111 functions to detect theposition of the permanent magnet 7 and let flow an effective currentthrough the single-phase permanent magnet motor 2 via the conversioncircuit 5. A current sensor 18 is included in the stator windings 10 ofthe single-phase permanent magnet motor or the conversion circuit 5. Thecurrent let flow through the stator windings 10 is always monitored bythe current sensor 18.

The control circuit 6 controls the conversion circuit 5 which suppliespower to the single-phase permanent motor, on the basis of informationof the position detector 111 and a current sensor 118, and previouslystored cogging torque information 113 and induced voltage information114.

An angle conversion unit 112 is a calculation unit for estimating anelectric angle θ of the rotor 4 on the basis of the information of theposition detector 111. The angle conversion unit 112 can calculate theaverage velocity of the rotor 4 on the basis of the period of thepositive-negative changeover of an output signal of the positiondetector 111, and calculate and estimate the angle of the rotor on thebasis of time elapse in the control period. Furthermore, thepositive-negative energization of the conversion circuit 5 is determinedby positive-negative information of the position detector 111.

FIG. 5 shows details of a principal part of the embodiment according tothe present invention. A pulsating torque calculation unit 116 includesan output torque calculation unit 117 for calculating output torque onthe basis of an output of the current sensor 118, an output of the angleconversion unit 112, the cogging torque information 113 and the inducedvoltage information 114, an average torque calculation unit 119 forcalculating an average value of an output of the output torquecalculation unit 117, and a pulsating torque operation unit 20.

Hereafter, a method for calculating the pulsating torque will bedescribed in detail.

Electromagnetic torque Tw(θ) which is generated by the magnetic fluxgenerated by the permanent magnet and a current which flows through thestator windings can be represented by using the following equation.

$\begin{matrix}{{{Tw}(\theta)} = \frac{{{EO}(\theta)}{I(\theta)}}{\omega}} & (4)\end{matrix}$

where

ω represents information of rotation angular velocity,

E0(θ) represents induced voltage information for an angle θ at eachvelocity ω, and

I(θ) represents current information obtained by the current sensor.

Therefore, total torque Tt(θ) generated by the single-phase permanentmagnet motor is represented by the following equation.

Tt(θ)=Tcog(θ)+Tw(θ)   (5)

Here, Tcog(θ) represents cogging torque for the rotation angle.

On the other hand, average torque Tav can be calculated according to thefollowing equation by finding an average of the total torque Tt(θ) overone cycle of electrical angle (which may be half a cycle as occasiondemands).

$\begin{matrix}{{Tav} = {\frac{2}{\pi}{\int_{- \pi}^{\pi}{{{Tt}(\theta)}{\theta}}}}} & (6)\end{matrix}$

Therefore, pulsating torque Tac(θ) can be represented by the followingequation.

Tac(θ)=Tt(θ)−Tav   (7)

In FIG. 4, the single-phase permanent magnet motor is typicallycontrolled by a velocity control unit 115 to follow a velocity commandNs. As described above, control is exercised by utilizing theproportional integral control or the like as occasion demands, on thebasis of velocity feedback information calculated from the period of onecycle of electrical angle of the position detector 111. On the otherhand, one cycle of the position detector 111 is divided finely toproduce a correction signal on the basis of pulsating torque informationcalculated by the pulsating torque calculation unit 116. Correctionsignals produced by the velocity control unit 115 and the pulsatingtorque calculation unit 116 are combined by a drive signal calculationproducing circuit 51 to control the conversion circuit 5. As a result,it is possible to flatten the output torque of the single-phasepermanent magnet motor by exercising correction control.

FIGS. 6A to 6H show operation explanation diagrams of theabove-described control according to the present invention.

FIG. 6A shows an output signal of the position detector 111. It is alsopossible to previously make the output signal lead the induced voltageshown in FIG. 6C. Velocity information of the permanent magnet rotor canbe calculated on the basis of the period of the signal over a half cycleor one cycle of the output signal of the position detector 111.

FIG. 6B is a terminal voltage of the motor. Basically, a positivevoltage signal is applied to a zero crossing point from negative topositive of position detector. The voltage height is regulated by thePWM (Pulse Width Modulation) or the like. It is also possible to makethe terminal voltage of the motor lead or lag behind the induced voltageshown in FIG. 6C by providing a delay from the zero crossing point by apredetermined time.

FIG. 6C shows induced voltage information as a function of the rotationelectrical angle. Typically, an induced voltage constant obtained bydividing the induced voltage by the rotation velocity is stored. Therotation velocity can be converted to the induced voltage by multiplyingthe rotation velocity by the induced voltage constant.

FIG. 6D shows current information taken in from the current sensor 118.The current information is successively measured and stored in thememory.

FIG. 6E shows cogging torque information as a function of the rotationelectrical angle. The cogging torque information is previously measuredand stored in the memory.

FIG. 6F shows electromagnetic torque Tw(θ) which is generated by themagnetic flux (induced voltage) generated by the permanent magnet and acurrent which flows through the stator windings. The electromagnetictorque Tw(θ) can be calculated by using the equation (4).

FIG. 6G shows total torque. The total torque is the sum of the torqueTw(θ) and the cogging torque as indicated by the equation (5).

FIG. 6H shows pulsating torque, and it is calculated by using theequations (6) and (7).

The drive signal calculation producing circuit 51 combines an output ofthe velocity control unit 115 and an output of the pulsating torquecalculation unit 116 to produce a signal for controlling the conversioncircuit 5. As a result of the control heretofore described, torqueripple in FIG. 6G is corrected and a single-phase permanent magnet motorcontrol apparatus with little torque ripple can be provided.

The above-described control is control of the fan and pump. The responsefrequency of the control is as low as several Hz. Therefore, control isexercised stably.

It is also possible to make the period of the velocity control equal toone electric cycle and conduct pulsating torque correction at an integertimes the period. Furthermore, it is also possible to stop the controlat the time of transition in largely changing the velocity command Nssignal as occasion demands.

As compared with an ordinary three-phase motor, only one set of windingsand one hall element are required in the single-phase permanent magnetmotor as shown in FIG. 4 (whereas three sets are required in the case ofthe three-phase motor). As for the conversion circuit as well, anH-bridge can be used. Therefore, the number of components also becomesfour, resulting in a great price merit. On the other hand, owing to theabove-described control, the operation torque can be flattened and a lownoise, low vibration permanent magnet motor control apparatus thatcompares favorably with the three-phase motor can be provided.

In the configuration heretofore described, the cogging torqueinformation 113 and the induced voltage information 114 are informationthat is proportional to square of the gap magnetic flux density orproportional to the gap magnetic flux density. The gap magnetic fluxdensity is information that is proportional to the temperature. If, forexample, a temperature sensor is provided in the single-phase permanentmagnet motor control apparatus and the cogging torque information 113and the induced voltage information 114 are corrected thereby,therefore, control with better precision can be exercised.

Furthermore, control with high precision is made possible by exercisingthe velocity control at half periods of electrical angle and dividingthe period into a plurality of parts to exercise pulsating torquecorrection control.

Considering precisions of constants and their dependence upon thetemperature as to the pulsating torque correction control, it ispossible to select the case where stable control can be achieved whenonly proportional control is exercised although a larger deviationremains as compared with zero deviation control using integral control.

It is possible to provide a low price, small-sized, light weight, lownoise, low vibration electromotive fan and electromotive pump with asimple configuration by adopting the single-phase permanent magnet motorcontrol apparatus in the electromotive fan and electromotive pump.

Yet another embodiment of the present invention will now be described.

FIG. 7 shows details of a principal part in the embodiment according tothe present invention. FIGS. 8A to 8I show operation explanationdiagrams of the embodiment according to the present invention.

The embodiment differs from the foregoing embodiments only in thepulsating torque calculation unit 116.

Pulsating torque shown in FIG. 8H can be calculated.

In the present embodiment, the pulsating torque is decomposed intofrequency components and control is exercised every frequency component.Herein, a method for reducing the torque ripple at two frequencies, forexample, at a frequency that is twice the fundamental wave in theelectrical frequency and a frequency that is four times the fundamentalwave will be described.

Basically, the ripple in the total torque can be reduced by calculatingthe phase and magnitude at each of two frequency components in thepulsating torque and exercising proportional integral control at each ofthe frequencies.

Hereafter, a concrete embodiment and operation will be described withreference to the drawings.

In the configuration shown in FIG. 7, the pulsating torque calculationunit 116 includes an output torque calculation unit 117 for calculatingan output torque on the basis of the output of the current sensor 118,the output of the angle conversion unit 112, the cogging torqueinformation 113 and the induced voltage information 114, and a pulsatingtorque operation unit 20 for calculating average torque of the outputtorque from the output torque calculation unit 17 and pulsating torquefrom an output of the output torque calculation unit 117. This pulsatingtorque can be decomposed as shown in FIG. 8I. A first calculation unit21 for phase and magnitude of a component corresponding to twice thefundamental frequency can calculate its phase and magnitude of thepulsating torque by using the Fourier integral. A first correctionsignal generation unit 22 for a component corresponding to twice thefundamental wave exercises control with the goal of the componentcorresponding to twice the fundamental wave set to 0 and therebygenerates correction torque for the component corresponding to twice thefundamental wave of the calculated pulsating torque. As a result, it ispossible to selectively suppress the ripple of the componentcorresponding to twice the fundamental wave of the pulsating torque.

As for the component corresponding to four times the fundamentalfrequency of the pulsating torque as well, a second calculation unit 23for phase and magnitude of a component corresponding to four times thefundamental frequency can calculate its phase and magnitude by using theFourier integral in the same way. In addition, a second correctionsignal generation unit 24 for a component corresponding to four timesthe fundamental wave exercises control with the goal of the componentcorresponding to four times the fundamental wave set to 0 and therebygenerates correction torque for the component corresponding to fourtimes the fundamental wave of the calculated pulsating torque. Inaddition, a correction signal synthesis unit 25 exercises control. As aresult, it is possible to selectively suppress the torque ripple of thetwo frequency components.

FIG. 8I shows torques of the components respectively corresponding totwice and four time the fundamental frequency obtained by analyzing thepulsating torque shown in FIG. 8H. Output components of the calculationunit for phase and magnitude of a component corresponding to twice thefundamental frequency 21 and the calculation unit for phase andmagnitude of a component corresponding to four times the fundamentalfrequency 23 are shown in FIG. 8H. As a result, it is possible to reducethe torque ripple by generating effective correction signals.

In general, vibration and noise generated in the electromotive pump andelectromotive fan are based on factors having relations of integer timesin electrical angle, in many cases. Therefore, it is considered that thepresent scheme capable of reducing the factors every frequency iseffective.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A single-phase position sensorless permanent magnet motor control apparatus for controlling a power converter which drives a single-phase permanent magnet motor, the single-phase position sensorless permanent magnet control apparatus comprising: a motor current measuring unit; a terminal voltage measuring unit; a correction unit for correcting an impedance drop in motor constants; and a calculation unit for finding an induced voltage to be obtained by control, wherein a polarity of a terminal voltage is determined on the basis of a value of the found induced voltage.
 2. The single-phase position sensorless permanent magnet motor control apparatus according to claim 1, wherein at time of start, a current is let flow through the single-phase permanent magnet motor to determine a direction of the terminal voltage.
 3. A single-phase position sensorless permanent magnet motor control apparatus for controlling a power converter which drives a single-phase permanent magnet motor, the single-phase position sensorless permanent magnet control apparatus comprising: a motor current measuring unit; a terminal voltage measuring unit; a correction unit for correcting an impedance drop in motor constants; and a calculation unit for finding an induced voltage to be obtained by control, wherein an energizing current is continuously controlled on the basis of a value of the found induced voltage.
 4. A single-phase position sensorless permanent magnet motor control apparatus for controlling a power converter which drives a single-phase permanent magnet motor, the single-phase position sensorless permanent magnet control apparatus comprising: a motor current measuring unit; a terminal voltage measuring unit; a correction unit for correcting an impedance drop in motor constants; and a calculation unit for finding an induced voltage to be obtained by control, wherein changeover between positive and negative parts of the terminal voltage is conducted at a position of a high absolute value of the found induced voltage.
 5. A fan and pump comprising the single-phase position sensorless permanent magnet motor control apparatus according to claim
 1. 6. A single-phase permanent magnet motor control apparatus for controlling a power converter to drive a single-phase permanent magnet motor which includes a rotor having permanent magnets and a stator having single-phase windings and which generates cogging torque by magnetic action between the rotor and the stator, wherein the single-phase permanent magnet motor control apparatus comprises cogging torque and induced voltage waveform information of the single-phase permanent magnet motor.
 7. The single-phase permanent magnet motor control apparatus according to claim 6, wherein a shape of a gap face of a stator core of the single-phase permanent magnet motor is made different according to a rotation direction.
 8. The single-phase permanent magnet motor control apparatus according to claim 6, wherein the single-phase permanent magnet motor control apparatus has a function of detecting a temperature and a function of correcting the cogging torque and induced voltage information according to the detected temperature.
 9. The single-phase permanent magnet motor control apparatus according to claim 6, wherein output torque and output power are calculated and subjected to frequency analysis, and control is exercised every frequency.
 10. The single-phase permanent magnet motor control apparatus according to claim 6, wherein a circumference direction is divided into a plurality of sections and control is exercised every section.
 11. The single-phase permanent magnet motor control apparatus according to claim 6, wherein the control does not comprise integral control.
 12. A fan and pump comprising the single-phase position sensorless permanent magnet motor control apparatus according to claim
 6. 